On 11/10/2010 02:20 AM, Jorge Miguel wrote: > Hi, > > I have an easy question. > When I use my basic T/Rx daughterboards I can tune the receiver to an > specific frequency. Since the basic T/Rx doesn't have any LO, I would > like to know where is physically that LO in the USRP2 motherboard. I > cannot find anything in the schematics. Where is it? Is that LO the > one which translates from IF (coming from the daughterboards) to real > base band? > > Thanks in advance, > Jorge > There is no "LO", per-se on the USRP2 motherboard, only the various digital clocks used by parts on the motherboard, including the ADCs/DACs, and the FPGA.
When you're using a BASIC_RX/LF_RX and you "tune", the FPGA uses a DDC (Digital Downconverter) to digitally downconvert your desired frequency range to baseband. On the USRP2, the BASIC_RX or LF_RX is sampled at 100MHz, so the FPGA "sees" from roughly DC to roughly 50MHz. Within that range, the FPGA DDC converts whatever you ask it to into a complex baseband, which is what the host computer sees. -- Principal Investigator Shirleys Bay Radio Astronomy Consortium http://www.sbrac.org _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
